The work proposed is based on the general premise that retinal diseases disturb the flow of information from absorbance of light by the visual pigments in the outer segments to the neural cells in the proximal retina. The work has two main lines. The first is to continue intensive investigations of older pediatric patients as they become available. Photon-counting densitometry, measurements of the Stiles-Crawford effect and Westheimer functions will be added to the probes of retinal function previously available in this laboratory. Longitudinal surveillance of ERG responses and dark adapted thresholds of patients less than 12 yrs having retinal degenerations with onset in infancy or early childhood will be maintained to develop descriptions of the natural history of these diseases. The second line consists of three sets of experiments designed to provide firmer foundations for interpretation of the patients' data. 1) A study of young highly myopic patients and emmetropic and hyperopic control subjects will concentrate of the effects of the eye's optics, photoreceptor optics and the dimensions of post- receptoral elements on visual pigment densities and sensitivities, and provide a background against which data from patients with retinal degenerations, many of whom are myopic, can be compared. 2) Young PCD mice and RCS rats, examples of retinal disease limited to the photoreceptors, and patients with early diabetic retinopathy, examples of proximal retinal disease, will have the relations of distal to proximal retinal function investigated to define the conditions in which the distal retina governs proximal retinal function, and the extent to which proximal retinal function depends upon perfusion by the retinal vasculature. 3) For young patients with retinal disorders, the dark-adapted thresholds obtained with a quick staircase procedure will be compared to those obtained using the method of constant stimuli. The overall goal is to develop deft probes that efficiently and precisely identify aberrations in the flow of retinal information. Identification of specific pathophysiology could assist in directing intervention to alleviate the effects of pediatric retinal disease.